Posts Tagged ‘exoplanets’
stuff about the Nancy Grace Roman space telescope
Roman in the purple haze
So I’m at a loss to find anything to write about, as often happens, as there’s nothing I’m really knowledgeable about, and global politics is generally too awful to take seriously, but I must needs keep writing, for what else am I good for?
This morning I’ve been listening to people at NASA or is it Goddard talking to informed members of the public about the Nancy Grace Roman Space Telescope, aka Roman, which I’ve vaguely heard about before, but this was all very exciting talk about it being launched around September, way ahead of schedule and under budget. So look out, dark matter, dark energy and the multiverse, here we come.
I’ve recently heard people I know – not the most sciencey people on the planet – going on about the Artemis missions as ‘been, there, done that’ and a money-wasting ‘nothingburger’, but given some of the shite happening here on Earth, one can’t help indulging the fantasy of getting away from it all. And I couldn’t help feeling a pang of envy for the Goddard people in their happy bubble of space enterprise. Beam me up, I say – or is it down?…
But the Roman really does seem a fantastical piece of machinery, worth exploring. First, though, who was Nancy Grace Roman? Well, sadly she died on Christmas Day, 2018 – a bit of a downer for the family, but then she was 93. She was an astronomer, and NASA’s chief of astronomy in the 70s, an important figure in planning the Hubble Space telescope, an educator, and an advocate for sciencey women, so, what with the Vera Rubin and the Just Wonderful Space Telescope (didn’t catch on, sadly), women are creeping closer to space dominance. The news conference I listened to was full of optimistic excitement and pride. The launch is set for September, for a Sun-Earth orbit at Lagrange point 2.
So, onto Lagrange points, which I used to understand, I think. They’re points of gravitational equilibrium between two massive orbiting bodies, in this case the earth and the sun. They’re a place of balanced forces, perfect for a relatively small body such as a spaceship, or a space telescope, to make a stable home. There are five Lagrange points in the orbital plane of the earth-sun system, which is standard for any such large body system. So, getting out of the earth’s atmosphere has obvious advantages for clear viewing, what with Rayleigh scattering, ozone absorbing UV light, and other problems.
The Roman is particularly an advance on the Hubble, as they’re similar types, with the Roman having a much wider field of view. And then there’s the Vera Rubin, which I’m sure I’ll get round to (this is all just a self-education vid).
But now for the coronagraph. From Wikipedia:
A coronagraph is a telescopic attachment designed to block out the direct light from a star or other bright object so that nearby objects – which otherwise would be hidden in the object’s bright glare – can be resolved.
I’m listening to/watching a video from three years ago featuring a Dr Vanessa Bailey, who is clearly very excited and also very knowledgeable about the Roman and its coronagraph – doubtless even more excited now as the launch date has been put forward to September this year, instead of 2017. It gets very technical for a know-nothing like me, but I intend to watch it more than once as well as reading up on coronagraphs and the Roman on Wikipedia etc. I feel something coming on as I try to process this stuff, a real sense of excitement, not so much about weird physics, massless particles, strangeness and charm, and the multiverse, but habitable planets, and exoplanets in general. No doubt Roman will be charged with duties other than exploring exoplanets, but the expansion of our exoplanet discoveries since the nineties has excited me more than anything else in astronomy.
So I’ve given Wiki’s brief description of a coronagraph above, and it’s clear from that description that coronagraphs will be key to locating and exploring exoplanets (6,273 confirmed as of April 23 2026, and many more yet to be confirmed, and AI never lies). Apparently the Roman will be equipped with a ‘next generation’ coronagraph – essentially there are two types, solar and stellar – and with the Roman it’s about stellar coronagraphs, which are intended to block or reduce light from all stars or bright objects other than the sun. The telescope itself is similar in size to Hubble, but Dr Bailey points out that Roman’s field of view will be such that it will be able to do ‘in one shot’ what would require dozens of shots from Hubble, and this wide field will help with exploring dark matter and dark energy. The coronagraph will have a one hundred-fold greater sensitivity than that of Hubble.
We get into heavy detail at this point, Fraser Cain, the interviewer, being way more nerdy – I mean expert – about this stuff than me, what with F-numbers (reference below), which have much to do with field-of-view and clarity, and gravitational lensing and its possible connection with dark matter, and other distortions.
So, the coronagraph. The whole purpose of this one is as a ‘technology demonstrator’. To quote Dr Bailey:
by the 2040s, NASA wants to be imaging Earth-like planets around nearby Sun-like stars to search for life – I mean, we’re talking single-pixel, very fuzzy images, we’re not talking continents and clouds, but even to be able to detect Earth-like planets at all, you’re trying to find something that’s ten billion times fainter than its host star – incredibly close at least in terms of its angular separation. What Hubble can do, in terms of its coronagraph, is on the order of a million times fainter – which is phenomenal, it lets us see young hot glowing Jupiters, that are still emitting plenty of light from the heat of their formation process, but that’s nowhere near what we need for those ‘exo-Earths’. So the Roman coronagraph is going to be an intermediate generation of instrumentation – we hope we’ll definitely achieve at least 10 million to one detection limits for a planet that’s 10 million times fainter than its star – our goal is to do 100 million to one, closer to a billion to one…
All of which sounds pretty exciting to me, except that I’ll be turning 90 around the middle of the 2040s – gotta get that little cough under control. Dr Bailey continued to detail aspects of the coronagraph which go way beyond my comprehension, having only looked through a basic little telescope once or twice in my life, a most pleasant memory. Apparently the Roman coronagraph will have around a hundred times the sensitivity of Hubble, which will presumably lead to far more habitable zone planets being detected and surveyed for any interesting anomalies or signs of – I dare not speak its name. and of course there will be other possibilities relating to dark matter and other mysteries. For example measuring the shapes and perhaps the more detailed activities of galaxies may throw more light onto dark matter, so to speak.
And of course I remember those first exoplanet discoveries in the 1990s, and the sudden knowledge, for me at least, that every one of the zillions of stars out there was a solar system. I’m not sure if Hubble was essential to those first discoveries, but it’s probable. A NASA website on Hubble is fascinating on this, so I’ll just quote:
For a long time, scientists thought that other planetary systems were likely to resemble our own. But humanity was in for an eye-opening revelation about what constituted a run-of-the-mill planetary system. The first exoplanet discovered was a “hot Jupiter,” or a Jupiter-like gas giant orbiting astoundingly close to its star ― only 5 million miles (8 million km). That’s closer than Mercury is to our Sun.
The variety of new types of planets that poured in were astounding. In addition to many hot Jupiters, astronomers found:
- Super-Earths: Rocky planets more massive than Earth, but lighter than Neptune
- Hot Neptunes: Neptune-size planets in tight orbits around their stars
- Mini-Neptunes (or sub-Neptunes): Roughly Neptune-size planets thought to have solid inner cores and dense helium-hydrogen atmospheres
- Ultra-hot Jupiters: Jupiter-like gas giant planets orbiting so close to their stars that their temperatures exceed 3,000 degrees Fahrenheit, hot to vaporize most metals
- Super Puffs: Young planets with the density of cotton candy. Their hydrogen/helium atmospheres are so bloated they are nearly the size of Jupiter, but their mass is only several times that of Earth
So, that’s enough excitement for now, and it’s only the beginning. This is something I hope to follow, if health allows.
References
NASA News Conference: Nancy Grace Roman Space Telescope is Complete
https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telescope
How Nancy Grace Roman’s Coronagraph Will Revolutionise Planet Hunting (Fraser Cain interview with Dr Vanessa Bailey)
Proxima b
Quote of the day/week/month/post:
Better to have questions you can’t answer than answers you can’t question – Max Tegmark (and many others)
Jacinta: So while astrophysicists argue over the likelihood of life elsewhere in our tiny but massive universe, some are focusing on our nearest star neighbour. Some wobbling of the red dwarf known as Proxima Centauri has revealed, upon lengthy observation, that it has a closely orbiting planet, which considering the relative coolness of the star – way too dim to be seen with the naked eye – and the proximity of its satellite, is very much in the habitable zone. While it’s too early to say so much for the naysayers, the discovery of a planet in the Goldilocks zone of our nearest star in a galaxy of billions of possibilities must surely raise hopes and expectations of life abundant.
Canto: This closest possible exoplanet was only discovered in August this year, so we’re desperate to find out more about it. Being in the habzone is one thing, habitability is another. Obvious questions we have no current way of answering are: does it have an atmosphere? Any possibility of water? Is it tidally locked? And of course we’d love to know if we could launch some sort of robotic mission to our nearest star neighbour. Meanwhile is there any other way of gleaning more info from this tantalising object?
Jacinta: It’s not likely to be habitable though. Solar winds are estimated to be some 2000 times those experienced on Earth, though we can’t be too sure. Researchers are trying to work out the size of the planet…
Canto: How do they know about those solar winds?
Jacinta: Oooh, that’s a horribly good question. It’s due to the closeness of the orbit, where you would expect the solar winds to be much stronger, as they are in our solar system. It’s believed that Mercury’s magnetic field, which should be stronger than it’s been measured to be because of its heavy metallic core, is dampened massively by our solar wind. So basically they would’ve inferred Proxima Centauri’s wind by our own. As to how they came up with the figure of 2000 times that experienced on Earth, I’ve no idea, but strong solar winds make it hard to maintain an atmosphere, which is vital for life. You’ve also talked about tidal locking, which is a feature of close orbits, such as the Moon’s orbit of the Earth. So you’ll have a permanently hot day side and a permanently cool night side, and this can be problematic for the creation of an atmosphere, according to modelling.
Canto: Now, all of this sounds very negative, but basing exo-planetary activity on what’s been the case, as far as we can work it out, in our solar system, has been really problematic hasn’t it?
Jacinta: Definitely, that’s why we need to go beyond modelling, if we can, and collect some real data. So we’re looking to the James Webb Space Telescope (JWST), the very exciting successor to Hubble to be launched around November 2018, to garner more info, which it’ll be perfectly equipped to do.
Canto: If by some near-miraculous combination of circs there is an atmosphere on Proxima b, or a reasonable quantity of liquid water, that would help distribute the heat around the planet. With no atmosphere, the difference between day side and night side would be stark.
Jacinta: Exactly, and that’s what the JWST should be able to detect, as the best way to detect the atmosphere is to measure the planet’s infrared heat signature. If the JWST finds a decisive and fixed difference between the planet’s day and night sides, it’s a safe bet that no atmosphere is present. The JWST will be equipped to measure this IR signature on both sides of the planet, and if it doesn’t find that stark difference, that’ll be when we can start speculating about an atmosphere and its constituents.
Canto: Though of course they’ve already started with the speculation. But really, whatever they find – and I don’t expect that everything will line up for life – the fact that we’ve found an exoplanet well worth investigating on the nearest star outside our solar system, with billions of stars yet to be homed in on, one by one – doesn’t that say something to those who argue for the Fermi paradox – where are they? Okay, Fermi and Hart were talking about intelligent life, and that may well be orders of magnitude more difficult to develop than life itself, but I’m sure that Fermi would be unsettled in his skepticism, if he was alive today, by the vast numbers of exoplanets, in other words possibilities for life, we’re discovering now, with so many to come in the near future.
Jacinta: Yes, bliss in this time it is to be alive, but to be young, that would be very heaven!
Cosmos issue 71, pp9-10
http://www.gizmodo.com.au/2016/08/how-well-get-our-first-big-clue-about-life-on-proxima-b/
en.wikipedia.org/wiki/Proxima_Centauri_b