Science Pics of the Week: NASA surveys raindrops from space
Meteorologist/Science Writer
Friday, April 1, 2016, 4:33 PM - Surveying raindrop sizes from space, mapping out the climate of a burning hot super-Earth and watching the history of our solar system unfold. It's Science Pics of the Week!
Surveying raindrops from space
From here on the ground, weather radar does an excellent job of showing us how much rain we can expect from passing weather systems. Apparently, though, according to the latest results from the NASA/JAXA Global Precipitation Measurement (GPM) mission, there's a much better vantage point on rainstorms to be found by going higher up.
This conceptual image shows how satellite scans of a storm can reveal the variation of size and distribution of raindrops within, ranging from the smallest (0.5-3 mm wide, in blues and greens) to the largest (4-6 mm in size, in yellows, oranges and reds). Credit: NASA/Goddard
Why image raindrop size from space?
"The drop size distribution is one of many factors that determines how big a storm will grow, how long it will last and how much rain it will ultimately produce," Joe Munchak, a research meteorologist at NASA’s Goddard Space Flight Center, said in a press release. "We’ve never been able to see how water droplet sizes vary globally until now."
According to NASA:
With GPM’s three-dimensional snapshots of drop size distribution, scientists can also gain insight into the structure of a storm and how it will behave. Drop size distribution influences storm growth by changing the rate of evaporation of rain as it falls through dry air, said Munchak. Smaller drops, for instance, will tend to evaporate faster and subsequently cool the air more. This leads to stronger flow of downward moving air that can cause damaging winds when they reach the ground. However, these same downdrafts can interfere with the upward flowing air that fuels the storm and cause the storm to weaken or dissipate.
Adding this kind of information to weather and climate models promises even more accurate forecasting in the future.
Mapping out the climate of an alien lava world
Astronomers using NASA's Spitzer Space Telescope, an infrared observatory, have captured new data on the hot super-Earth planet 55 Cancri e, located about 40 light years away.
Orbiting its Sun-like star at a distance just 2.3 million kilometres (4 per cent the distance Mercury is from our Sun), the planet apparently hot enough to melt rock on one side (around 2,400oC) and noticably cooler on the dark side (1,100oC).
This artist's conception animation shows 55 Cancri e's day and night sides as the planet orbits around its star every 18 hours. Credit: NASA/JPL-Caltech
According to NASA:
This planet is tidally locked to its star, just as our moon is to Earth, which means that one side always sizzles under the heat of its star while the other side remains in the dark. If the planet were covered in lava, then the hot, sun-facing side of the planet would have liquid lava flows, while the colder, dark side would see solidified lava rock. The hardened lava would be unable to transport heat across the planet, explaining why Spitzer detected that the cold side of the planet is much colder than the hot side.
Such a lava planet, if it exists, would have dust streaming off of it, as illustrated here. Radiation and winds from the nearby star would blow off the material.
The image below shows how the planet's brightness (and thus temperature) varied over time to Spitzer. A curious aspect of the light curve is that it reached its brightest (thus hottest) a few hours before the planet ducked behind the star. If the planet's hottest part was directly facing the star, the light curve would continue to increase until the planet was lost from sight, and would pick up again at around the same brightness when it reappeared on the other side.
Credit: NASA/JPL-Caltech/University of Cambridge
The researchers studying the Spitzer data believe that the greatest source of heat on the day side is offset, possibly due to large lava flows on the surface.
Watching our solar system's history unfold out in space
Around 175 light years away from us, there's a very young star named TW Hydrae, which is fairly remarkable because it is spinning nearly perpendicular to the Sun's rotation. This means that by looking at this star through telescopes, we are seeing it, and its disk of planet-forming gas and dust, from a nearly top-down vantage point.
When astronomers with the European Southern Observatory (ESO) recently pointed the radio antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) at TW Hydrae, they captured this remarkable image.
Credits: S. Andrews (Harvard-Smithsonian CfA); B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO)
According to the ESO:
"Previous studies with optical and radio telescopes confirm that TW Hydrae hosts a prominent disc with features that strongly suggest planets are beginning to coalesce," said Sean Andrews with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, USA and lead author on a paper published today in the Astrophysical Journal Letters. "The new ALMA images show the disc in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that may indicate that a planet with an Earth-like orbit is forming there."
Other pronounced gaps that show up in the new images are located three billion and six billion kilometres from the central star, similar to the average distances from the Sun to Uranus and Pluto in the Solar System. They too are likely to be the results of particles that came together to form planets, which then swept their orbits clear of dust and gas and shepherded the remaining material into well-defined bands.
Given that TW Hydrae is only around 10 million years old, observing the star and the planets that are apparently forming around it, is giving astronomers insights into what our own solar system may have been like, billions of years ago.
Watch it again: Based on the motions of objects out beyond the orbit of Pluto, astronomers believe that there may be another large planet out in the distant reaches of our solar system.
