Space Sunday: planets, stars and spacecraft

Artist’s impression of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. Credit: ESO/M. Kornmesser

Proxima b, the planet discovered orbiting the closest star to our own, Proxima Centauri (see here for more), has been the subject of much speculation regarding its potential habitability (see here for more). Now a new study is underway which may bright us a lot closer to understanding the conditions on the planet.

Located 4.25 light years away, Proxima Centauri is a M-type red dwarf star. Such stars are highly variable and unstable compared to other types of stars, and this might weigh heavily against Proxima b having the right conditions for life to arise. The new study involves a team of astrophysicists from the University of Exeter, England, and staff from the UK’s Meteorological Office, who have been using the latter’s state-of-the-art Unified Model (UM).

This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Credit: ESO

Used to study Earth’s atmosphere, with applications ranging from weather prediction to the effects of climate change, the Unified Model allowed the team to simulate what Proxima b might be like if it had a similar atmospheric composition to Earth, and also what it might be like if had a much simpler atmosphere – one composed of nitrogen with trace amounts of carbon dioxide. Last, but not least, they made allowances for variations in the planet’s orbit.

This last point is important because given the planet’s distance from its parent – around 7.5 million km (4.6 million mi) – Proxima b is likely to either be tidally locked so that one face constantly faces its sun, or it is in a 3:2 orbital resonance, rotating three times on its axis for every two orbits around its sun. In the former situation, the main atmospheric gases on the night-facing side would likely freeze, leaving the daylight zone exposed and dry; in the latter, a single solar “day” would last a long time, resulting in the sunward side of the planet being extremely hot and day and the night side very cold and dry.

Taking all of this into account, and using data from previous studies, the UK team found that Proxima b, with either a complex or a simple atmosphere, could have regions where water might exist in liquid form. In addition, any substantive eccentricity in the planet’s orbit around its sun could further increase its potential habitability.

It will still be some time before more can be directly discerned about Proxima b, but it is hoped that the study will help in our understanding of the potential habitability of other exoplanets, and demonstrates how the study of conditions here on Earth can be used to predict what may exist in extra-solar environments.  It may also improve our understanding of how our own climate has and will evolve.

US Military “Close” To Awarding Spaceplane Contract

The US Defence Advanced Research Projects Agency (DARPA) is reportedly “close” to awarding a contract to build its XS-1 spaceplane launch vehicle.

An artist’s impression of the Boeing XS-1 concept vehicle

Announced in 2013, the XS-1 is intended to provide the US military with the means to rapidly deploy small satellite payloads to Earth orbit using a re-usable first stage and expendable upper stage which may be carried piggyback by the first stage vehicle. The goal of the programme is to provide an uncrewed launch vehicle capable of delivering payloads of up to 2,300 kg (5,000 lb) to orbit, which can be rapidly re-used – the target of the development programme is to have the vehicle complete 10 launches in 10 days. In addition, the vehicle must:

  • Be capable of hypersonic flight to Mach 10 (12,250 km/h) or higher
  • Lifting an expendable upper stage unit which it can then launch, and which can carry the payload to orbit
  • Operate with a launch cost less than 1/10 that of current launch systems (i.e. around US $5 million per flight).

Three groups of companies were awarded initial design concept contracts:  Boeing and Blue Origin, Masten Space Systems and XCOR Aerospace, and Northrop Grumman and Virgin Galactic. None of these may be awarded the development contract, which is intended to see the project to a point where test flights could commence in 2020.

To be successful, the vehicle will make use of advanced materials, cryogenic tanks, durable thermal protection, and modular subsystems. These, coupled with a reliable, re-usable propulsion system, would make it possible for the vehicle to achieve the hoped-of low-cost, rapid launch and re-use capability.

Tabby’s Star is at it Again

In October 2016, I wrote about “Tabby’s Star”, more formally known as KIC 8462852, an F-type main-sequence star located in the constellation Cygnus approximately 1,480 light years from Earth.  It came to prominence in 2015 after data gathered by the Kepler exoplanet mission revealed it is experiencing massive and irregular dips in brightness of up to 22% at a time, which last for several days before the star reverts to its “normal” brightness once more.

Fluctuations in the brightness of some stars isn’t that unusual, and can be down to a number of reasons. Kepler, for example, looks for regular dips in a star’s brightness which might be the result of a planet moving between the star and itself. However, the sheer magnitude of the fluctuations experienced  by Tabby’s Star were beyond anything previously seen, making it the subject of intense interest to professionals and amateurs alike, while prompting all sorts of theories on what might be causing the fluctuations – up to and including the presence of alien megastructures around the star, as I noted last time around.

Artist’s concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA, JPL-Caltech

The problem is, the cycles of dimming aren’t regular, making predicting when they might occur difficult, and on one observatory can keep an eye on “Tabby’s Star” all the time, and this in turn makes identifying a possible cause extremely hard. However, at the end of April, the Fairborn Observatory in Arizona noted the possible start of another cycle, prompting astronomers to watch the star. Then, on May 18th / 19th, 2017 and in the space of one night, “Tabby’s Star” dimmed by 2%, resulting in a world-wide call to astronomers to turn as many telescopes as possible toward the star, to try to crack the mystery of its behaviour.

The hope is that whatever is causing the star to get dimmer will leave a spectral fingerprint behind. So if the dimming is cause by a dust cloud passing between the star and Earth, it should block more blue light than red light; If there’s gas in that dust, it will absorb very specific wavelengths, etc. These changes will be reflected in the light spectra recorded by observatories, allowing astronomers to identify any natural phenomenon which might be responsible for the star’s fluctuations.

Nor is it purely astronomical observatories watching – or listening – to Tabby’s Star. The Breakthrough Listen initiative, which searches for signs of intelligent life in the universe, has also taken an interest in the star and will be observing it with the Automated Planet Finder telescope at Lick Observatory in California – just on the off-chance aliens might be doing something around the star!

Regardless of any ideas of aliens and megastructures, observations of the current dimming cycle at “Tabby’s Star” will hopefully provide insight into what is happening there.

In Brief

  • Virgin Galactic has announced that seats aboard it’s sub-orbital SpaceShipTwo vehicle are now “fully booked” through until 2021, assuming commercial operations start in 2018 as is the hope. To date, over 650 tickets for flights aboard the vehicle, costing around US $250,000 apiece, have been sold.
  • NASA’s Juno mission completed the latest of its close passes around Jupiter on May 19th, 2017, coming to within 3,500 km (2,200 mi), marking it as one of the closest approaches the vehicle has made to Jupiter since Juno arrived at Jupiter on July 4th, 2016. The flyby was celebrated by NASA with the release of a series of images captured by the spacecraft made a close pass of Jupiter on February 2nd, 2017. Including a close-up of the “Little Red Spot”, a storm akin to Jupiter’s famous Great Red Spot.
A colour enhanced image of Jupiter’s Little Red Spot imaged by the Juno spacecraft on February 2nd, 2017 (and released May 18), produced by citizen scientist Bjorn Jonsson using data from Juno’s JunoCam instrument. Credit: Bjorn Jonsson / NASA/JPL / SwRI / MSSS
  • NASA is likely to see around US $560 million cut from its 2018 budget when it is announced on May 23rd. The overall funding for NASA will be around US $19.092 billion, with the cuts being spread throughout multiple NASA programmes. Earth sciences are likely to see their budget cut by US $121 million; the Orion  / SLS programme will likely be cut by US.
    $200 million, while operational funds, which cover the space station, crew transportation to / from the ISS, and commercial resupply missions, will be cut by US $210 million.
  • The United States Senate’s space subcommittee is considering making changes to the 50-year-old Outer Space Treaty, potential to assist with commercial space operations.
    The Treaty allows any nation that is a party to it to propose amendments, which enter force for those agreeing to them once a majority of the nations who have ratified the treaty do so. currently, 105 nations are signatory to the agreement. Mark J. Sundahl offers an interesting op-ed on the subject.