That green streak in front of the Andromeda galaxy is a meteor. While photographing the Andromeda galaxy in 2016, near the peak of the Perseid Meteor Shower, a sand-sized rock from deep space crossed right in front of our Milky Way Galaxy’s far-distant companion.
The small meteor took only a fraction of a second to pass through this 10-degree field. The meteor flared several times while braking violently upon entering Earth’s atmosphere. The green color was created, at least in part, by the meteor’s gas glowing as it vaporized.
Although the exposure was timed to catch a Perseids meteor, the orientation of the imaged streak seems a better match to a meteor from the Southern Delta Aquariids, a meteor shower that peaked a few weeks earlier.
What lies beneath the layered south pole of Mars? A recent measurement with ground-penetrating radar from ESA’s Mars Express satellite has detected a bright reflection layer consistent with an underground lake of salty water.
The reflection comes from about 1.5-km down but covers an area 200-km across. Liquid water evaporates quickly from the surface of Mars, but a briny confined lake, such as implied by the radar reflection, could last much longer and be a candidate to host life such as microbes.
Pictured, an infrared, green, and blue image of the south pole of Mars taken by Mars Express in 2012 shows a complex mixture of layers of dirt, frozen carbon dioxide, and frozen water.
Image Credit & License: ESA/DLR/FU Berlin; Bill Dunford
The striking blue color of the Iris Nebula is created by light from the bright star SAO 19158 reflecting off of a dense patch of normally dark dust. Not only is the star itself mostly blue, but blue light from the star is preferentially reflected by the dust — the same effect that makes Earth’s sky blue.
The brown tint of the pervasive dust comes partly from photoluminescence — dust converting ultraviolet radiation to red light. Cataloged as NGC 7023, the Iris Nebula is studied frequently because of the unusual prevalence there of Polycyclic Aromatic Hydrocarbons (PAHs), complex molecules that are also released on Earth during the incomplete combustion of wood fires.
The bright blue portion of the Iris Nebula spans about six light years. The Iris Nebula, pictured here, lies about 1300 light years distant and can be found with a small telescope toward the constellation of Cepheus.
Image Credit & Copyright: Franco Sgueglia & Francesco Sferlazza