Amateur Astronomy


The story of the moment - liquid water found on Mars.

How quickly can Mars rovers be launched ?


Ones that can survive at Mars’s south pole and drill 1.5 km below the surface … probably not very quick? :smiley:

Whole different ballgame from trundling around a Martian desert sniffing rocks, at less than five degrees from the equator.

Think of the concerns about drilling Antarctic Lake Vostok and the possibility of contamination. Then multiply by a million.


Darn this country! There is skanky weather due on Friday, with just a hint of a possibility that eclipse time on the east coast might fall in a clearance between two bands of rain. Still keeping my hopes up. I did a reccy down Dun Laoghaire pier tonight just about Mars rise time, and the viewing was awesome. (P.S. The bandstand is fenced off for renovations).

Ok, my vintage iPhone is somewhat less than awesome, so here’s what I could actually see:

Four out of five of the classical planets all above the horizon simultaneously! It was the first time I got a sense of the ecliptic (the plane of the solar system orbits) as a real line in the sky. On Friday the eclipsed moon will have moved over left to above where Mars is.

If only tonight was Friday! :unamused: :frowning:


it looked amazing as well tonight not too far away about 1.5km inland, mars looks like a copper spot.
Was unaware that was Saturn by the moon, thanks!

When the moon is higher up in the sky then the ecliptic plane looks ecliptier :astonished:


I thought the planets looked pretty cool skirting low to the horizon. But for a decent telescopic view, definitely, you want them high in the sky. Have to wait for winter for that, unfortunately. That’s something I’ve never thought to inquire about – how often do the superior planets come to opposition when the ecliptic is high in the night sky? A bit of Googling/Stellariuming required, methinks.


Massive discovery or super massive discovery? … 24741.html


Didn’t they already verify the gravitational red shift nearly sixty years ago in the Pound-Rebka experiment? Not to mention with sounding rockets, GPS and white dwarf spectra. I guess black hole measurements are sexier. :smiley:

I’m being a bit ungenerous. This is pretty awesome. They had to calculate the orbit of S2 in three dimensions. The radial velocity is easy because spectroscopic measurements are exquisitely sensitive to that. The proper motion, i.e. the change in angular position on the sky, is a different ball game. At a distance of 26 kly to the galactic centre, the motions are tiny even at S2’s perihelion speed of 8000 km/sec. What’s more, the centre of the galaxy is invisible at optical wavelengths, and the longer wavelengths that can penetrate dust give worse angular resolution.

So they used the interferometric capabilities of the VLT, combining infrared signals from four telescopes and combining them to give a single sharp image. Interferometry is easier with long wavelength radio waves. At short wavelengths they have to be incredible careful about the timing of the light paths from the four telescopes, for which they use mad techniques like stretchy optical fibres to compensate. This is all done by the GRAVITY instrument on the VLT, using which they were able to measure nightly movements of S2 on the sky. That’s pretty amazing given it’s a quarter of a million trillion kilometres away, the equivalent of spotting a euro coin on the moon. The paper is here.


Yay! What an achievement! Don’t think about that deep crack running along the outcrop you’re standing on. Oh, and don’t look down … you’re at the top of the world’s highest sheer drop, being 4100 ft from top to bottom, with the cliff overhanging by fifteen degrees on average. Beyond that it’s another 600 ft down to the Weasel River on the valley floor, with boulders the size of cars regularly crashing down the lower slopes.

Yet the description in the Canadian Alpine Journal of the first ascent of Mount Thor on July 21st 1965 sounds like a mere saunter for Lyman Strong Spitzer. He took it in on a solo hike down the Weasel Valley and Pangnirtung fjord on Baffin Island. The local Inuit hamlet is 50 km away and has been populated for thousands of years but is so remote that it had only encountered its first white Europeans forty years earlier. Spitzer was no spring chicken on this hike either, having turned 51 the month before.

If it is apt that ‘Strong’ was Spitzer’s middle name, his given name of ‘Lyman’ seems even more fortuitous. The Lyman series is coincidentally the name of a set of high energy ultravolet lines in the spectrum of hydrogen. And, as well as a mountaineer, Lyman Strong Spitzer was both an astronomer and physicist with a professional interest in high energy plasmas. You could say he wrote the book on it – his 1956 work, The Physics of Fully Ionized Gases, is still of interest to physicists doing fusion research.

Five years earlier Spitzer had invented the stellarator which was one of the earliest concepts in fusion machines. This was part of Project Matterhorn, a top secret Cold War project which – when declassified in the 1960s – became the Princeton Plasma Physics Laboratory. PPPL today is developing the spherical tokamak which is considered one of the more promising of many the fusion approaches under development.

Even earlier in the mid 1940s Spitzer developed the concept of a space-based telescope. This was more than a decade before Russia launched the first puny Sputnik. Spitzer’s idea was the direct inspiration for the Hubble Space Telescope, although it would not launch until nearly half a century later. He further developed the idea for NASA in the 1960s and he lived to work with data collected by the telescope itself in the 1990s.

It’s impossible to do Spitzer justice in a short article. He’s one of those thinkers whose ideas were taken up by other people and thus influenced scientific developments over entire generations. His many associations read like a who’s-who of 20th century physics and astronomy. He was inspired by Jeans and Eddington. He studied under Harlow Shapley and Henry Norris Russell who is the ‘R’ in the H-R diagram, probably the most important single tool for astrophysicists. He collaborated with John Archibald Wheeler on fusion research. He conceived of the idea of the interstellar medium (and wrote the book on it) and reasoned that it must be still generating stars today. My own introduction to the subject was written by Bruce Draine, one of Spitzer’s younger associates at Princeton. For a slightly more technical overview of Spitzer’s achievements you can download a short biography here.

It seems entirely fitting that one of NASA’s so-called Great Observatories was eventually named after Spitzer himself. This series of telescopes – Hubble, Compton, Chandra and Spitzer – observe the sky at optical, gamma ray, X-ray and infrared wavelengths respectively. It is traditional for NASA telescope missions to be given their final names only after they are successfully launched and commissioned. The telescope that became Spitzer went through many concept iterations and design changes. Back when the space shuttle was going to be “the bus to space”, it was intended to launch an infrared observatory that could be regularly fetched back down for refurbishment and replenishment of its cryogenic tanks. An infrared scope needs to be kept extremely cold so that its own emissions don’t swamp the infrared signals it is trying to capture.

When it became obvious that the shuttle would fly somewhat less regularly than weekly, Spitzer was redesigned for a once-off deployment from the shuttle. However, it needed an additional engine to boost it into its intended orbit around the Sun. After the Challenger disaster this component was considered too dangerous for carriage aboard the shuttle. Ultimately the telescope was launched in 2003 atop a Delta rocket, for a planned 30-month mission. Fifteen years later it is still going strong, although it’s cryogenics are exhausted and it can only observe at shorter wavelengths in the “warm phase” of its mission.

The very first commissioning image taken by Spitzer shows the value of space-based infrared astronomy. At optical wavelengths the Elephant’s Trunk nebula, seen below centre in the following image, appears as a dark dusty blot within a much larger region of ionised gas.

But in Spitzer’s infrared image the Elephant’s Trunk is seen glowing in its own emitted light, and several dust shrouded stars become visible. It turns out that the edge of the Trunk is being ionised by ultraviolet radiation from a nearby star which gives rise to the outline glow you can see in the optical. But the Trunk is also pressured from within by young stars with newly developed stellar winds which are trying to blow away the surrounding gas and dust. The enhanced pressure is triggering another wave of star formation which gives rise to a number of protostars caught in the act of being born. Only in the infrared can we see this flurry of activity in what would otherwise be a featureless and opaque hole in the sky.

Nowadays the infrared is an essential tool in the astronomer’s kit. Without it we would never see the youngest stars, which are invariably born inside thick obscuring clouds. These must be both dense enough and cold enough to allow gravitational collapse. We wouldn’t see the dusty protoplanetary discs forming new planets from the remains of the stellar nebulae. We’d never have seen through the Milky Way’s dust lanes to the galactic centre, or discovered its family of stars in tight orbits around a supermassive black hole. In colliding galaxies or in other galaxies with actively feeding black holes we wouldn’t see the massive dust torus with its vast infrared energy output. The brightest of these – the luminous, ultraluminous, and hyperluminous infrared galaxies (LIRGS) – can be from a hundred billion to a hundred trillion times as bright as our Sun, but with almost all the energy in IR.

Composite image of the Sombrero galaxy made by Hubble and Spitzer space telescopes. The Spitzer Infrared Nearby Galaxies Survey (SINGS) surveyed 75 galaxies to look at processes such as star formation. It revealed the giant eliptical halo of the Sombrero galaxy, the structure of its beautiful dust lanes, and the giant black hole lurking at its centre.
HH 46/47, a young stellar object ejecting a supersonic jet and creating a bipolar outflow. The central protostar lies inside a “Bok globule,” hidden from view in the visible-light image (inset). Before the Spitzer space telescope only a handful of nearby examples of this early stage of stellar evolution were known.

Our own planet and its atmosphere glow in the infrared at various wavelengths. It’s why we need to get above them to stare out into the cold of space. But we can also point space-based telescopes back at ourselves to see and measure aerosols in the air, and patterns of vegetation growth on the ground. These earth sensing applications are yet another extension of the brilliant idea that Lyman Strong Spitzer wrote about seventy years ago. Last week his eponymous telescope celebrated its birthday and entered its sixteenth year of space operations. We can be certain that Spitzer the man would have been delighted to see his brainchild coming of age.

A five minute video biography of Spitzer from Caltech
Launch of the Spitzer space telescope in August 2003

A compendium of Spitzer images released as a digital calendar by NASA on the telescope’s 12th birthday.
Full disc composite from GOES-R satellite shows the value of infrared in mapping Earth’s vegetation.


For anyone interested in contemplating our place in the universe, it always seemed to me that one of the hardest things about astronomy is developing an intuition for the distance scales involved. It’s really a hierarchy of scales, for example the size of the earth, the distance to the moon, the scale of the solar system, the distance to the nearest stars, the scale of the galaxy, of galaxy clusters, and eventually the whole observable universe. Of course you can write out all those scales just by adding strings of zeros, but I suggest that doesn’t really provide any intuitive grasp. Perhaps the scales are just too vast for human intuition, yet it seems to me that it can be of some help to just hold a few critical numbers in your head and practice a bit of mental arithmetic to translate from one scale to an adjacent one.

In this hierarchy of scales, I think the hardest one to contemplate is the distances between stars. It is by far the largest ratio of distance to the sizes of the objects themselves. The following video is pretty helpful …

He doesn’t mention it, since it’s hard enough to deal with just the closest stars, but if our Sun was the size of a pea the galaxy’s diameter would be a dozen times our distance from the Moon! But then, if our galaxy was the size of a pea, the entire observable universe would be only a kilometre across. The distance-to-object scale doesn’t necessarily get bigger as you go up the scales.

By the way, that vid’s little historical interlude about how we first figured out the absolute scale of the solar system from known ratios is fascinating in itself. In fact, there’s a much longer history in which Hipparchus measured the distance to the Moon by parallax in the 2nd century BC. Aristarchus attempted to acquire the distance to the Sun by geometrical means, but was let down by inaccurate measurements. In 1673 Cassini measured the position of Mars against background stars while his friend Richer did the same from French Guiana, obtaining the size of Mars’ orbit to within 7%. Newton and Halley described the means by which the solar distance could be acquired by parallax during a transit of Venus, but it had to wait until a suitable transit occurred – there are only a couple per century – and an expedition could be planned. Transits of Venus come in pairs separated by eight years, and by combining observations from two transits of 1761 and 1769, the French astronomer Jerome Lalande eventually obtained the distance to the Sun, accurate to 3%. But the distances to the stars are so large that the angular precision required for parallax measurements was not achieved until the 19th century, even when using the Earth’s entire orbit around the Sun as the baseline. Calandrelli reported an annual parallax movement of Alpha Lyrae in 1806, and the first actual distance measurement was achieved in 1838 when Friedrich Bessel obtained a parallax distance for 61 Cygni to within 10%.


ps200306, have you heard any news on TESS ?
Launched in April. But I think it’s been operational since June.
Should have picked up plenty of planets since.
Have you read any announcements ?


Well, I’m tempted to say lmgtfy :laughing:

But thanks for the reminder. Yeah, looks like they dished out the first list of candidate planets last week.

Earlier there were some nice images from the commissioning tests at the start of science operations in July:


I did ye bastard, but couldn’t find anything ! :stuck_out_tongue:

Is that a planet on the left hand side ?
The comet seems to pass behind it.

edit: Ahh it’s Mars.


The pointer at around 1:05 seems to suggest Mars is right of centre. Not sure which thing you are referring to that the comet passes behind but if I’m looking at the right thing it’s one of the variable stars. How can a comet go behind a star? It can’t, but I suspect the coma of the comet is massively over-exposed. We continue to see the star through it until it’s briefly eclipsed by the nucleus.


We will soon be at the 50th anniversary of what was to me the single most memorable of the Apollo missions - Apollo 8 going around the moon at Christmas 1968. I remember this mission having a far bigger impact on me at the time than any of the other missions. The big moment for Apollo 11 happened at 4am BST, which only the adults stayed up to watch. So for kids Apollo 11 was a bit of a bust. The Apollo 8 mission was better timed so the coverage was interspersed with usual Christmas Eve and Christmas Day TV programmes. Which were a much bigger deal back then. I remember the short news updates from the moon orbits just really adding to the whole magic of that week. 1968 had been a really terrible year, this was even obvious to us kids at the time based on how often the adults looked grim while watching and talking about the current news, but for that Christmas week the carnage of the rest of the year was forgotten. If only for a few days.

This mission also had what is to my mind the single most profound and moving moment of the whole space exploration enterprise. When the crew of Apollo 8 read the first few dozen verses of the Book of Genesis as their Christmas message to those back on planet Earth.

Somehow I dont think this particular moment will ever be topped.

This was also the Apollo mission that gave us the single most iconic image of the 1960’s…

So much happened 50 years ago in space, so little, relatively speaking, has happened since.


+1. My favourite extraterrestrial image by a long shot. I bought a big framed version of it many years ago.

As far as manned space flight is concerned, maybe. Personally I don’t much see the point of it. As far as practical science is concerned, the golden age of space exploration only started in the 1970s and has been accelerating ever since. As much as I take my hat off to the Apollo era and its legacy, I’d take in preference the Pioneers, Vikings, Voyagers and everything that came after them any day.


When did progress end jmc?
About 1972?
From your post it would seem that’s it’s all been downhill


There has been some amazing stuff the last few decades, the recent Pluto mission being a great example, but these have been engineering triumphs, and celestial mechanics triumphs, rather anything that reaches the heroic and inspiring heights of the first two decades. Plus on a straight bang per buck criteria, its been a bust for science. The politics of NASA and ESA programs has more in common with the Dept of Defense procurement programs than straight science research projects. Which themselves are not exactly the model of efficiency when it comes to the Big Science projects. For the last three decades or so the science tends to be the justification for keeping the technology infrastructure ticking over, most of which is duel use, rather than as any primary goal. The Hubble / KH11 fiasco being a classic example. The cost of just the repair mission on its own for the primary spherical aberration balls up with the Hubble was greater than the cost of building and running the Keck telescopes during their lifetime plus there would have been enough left over for a permanent research group of several dozen to work on the telescopes. The Kecks are far better telescopes but as they dont have a full time PR staff you dont hear much about them in the media.

Repeat and rinse, many times, over the decades.

As I said, really impressive engineering but inspiring and heroic deeds, like the early days, not at all. Which I suppose is reflected by the people one runs into nowadays who work for NASA. Exactly like all the other folk who work for defense contractors or Lawrence Livermore / DOE. Nice enough, but pretty mundane. Cannot imagine anyone like a George Mueller working for NASA nowadays.

Great science tends to be done by larger than life characters. Of which there were quite a few in the early days of NASA and various battling Russian space bureaus. Mundane bookkeeping tends to be done by bureaucratic organizations. Which is what all the current space agencies are. By and large. Any useful science generated happens despite rather than because of those organizations.


An interesting video where they mention the difficulties in speed needed to reach the sun




The heroics of the space race were hugely amplified by the accompanying propaganda campaign. And it sucked up an amazing nearly 5% of US GDP in the mid-sixties. I think I prefer today’s scientific heroes.

Sure, spending on space has very little to do with the planetary exploration and astronomical aspects of “space science”. It’s very hard to separate the scientific from the military/commercial since budget figures are often lumped together. But true spending on science is relatively modest.

I get the point, but it’s an almost impossible comparison to do. There were five servicing missions to the HST. If you cost them at the average cost per launch of the whole shuttle program, they were about a billion dollars each. At the incremental cost per launch it was only in the tens of millions. The HST and the Kecks each do certain things that the other can’t do – such as spectroscopy down to 112 nm in the ultraviolet by the HST which will always be the preserve of space-based instruments. I’m not arguing for ultra-expensive space telescopes but they have their place if they can be done cheaper. The HST has itself been used in quite a propagandistic way. Who has even heard of the other three telescope in the NASA Great Observatories program even though they are equally scientifically crucial?

But wasn’t Mueller’s greatest success as an administrator, forcing reorganisation of NASA? There are certainly larger than life characters in science, but I definitely don’t think that all (or even most) great science is done by them. The ones that seem larger than life are media inventions (like Einstein) or self-promoters (like Hubble).

Anyway, not entirely disagreeing, just not wearing any rose-tinted glasses from the 1960s. The bit of science that I’m most interested in – astronomy – has definitely been in a continuously improving Golden Age for decades. Manned spaceflight enthusiasts will obviously see it differently.