The Sky this Week: July 3–12, 2015
Your daily digest of celestial events coming soon to a sky near you.
Venus (the brighter of the two) and Jupiter continue to dazzle together in the evening sky, just as they did in this image from June 29.
Steve Irvine
Friday, July 3
Although Venus and Jupiter appeared within a Full Moon’s width of each other the evenings of June 30 and July 1, the two brightest planets remain close this week. Tonight, you can find Jupiter, the second-brightest point of light in the sky, 1.4° to the right of its brighter companion. The gap will grow a bit, to 5°, by week’s end. The two appear about 20° high in the west a half-hour after sunset and don’t dip below the horizon until 10:45 p.m. local daylight time. A telescope shows both of their disks: Jupiter’s measures 32" across while Venus’ spans 34" and appears 32 percent lit.
No holiday better epitomizes summer in the United States than Independence Day. And the season’s namesake asterism — the Summer Triangle — will be on prominent display as fireworks ring out across the land. The trio’s brightest member, Vega in the constellation Lyra the Harp, stands nearly overhead in late evening. The asterism’s second-brightest star, Altair in Aquila the Eagle, then lies about halfway from the southeastern horizon to the zenith. Deneb, the luminary of Cygnus the Swan, marks the Summer Triangle’s third corner. Although it is this asterism’s dimmest star, it’s the brightest point of light in the northeastern sky.
Sunday, July 5
Asteroid 2 Pallas appeared opposite the Sun in mid-June, and it continues to linger in the sky all night. The magnitude 9.5 object — the second-largest body located between the orbits of Mars and Jupiter — lies among the background stars of Hercules, a region that climbs nearly overhead in late evening. Using binoculars or a telescope, first locate magnitude 3.1 Delta (δ) Herculis, the constellation’s third-brightest star. Pallas lies 0.6° southwest of this star tonight. If you are unsure which point of light is the asteroid, sketch the field and return to it a night or two later. The object that moved is Pallas.
The Moon reaches perigee, the closest point in its orbit around Earth, at 2:52 p.m. EDT. It then lies 228,101 miles (367,093 kilometers) away from us.
Although Venus and Jupiter appeared within a Full Moon’s width of each other the evenings of June 30 and July 1, the two brightest planets remain close this week. Tonight, you can find Jupiter, the second-brightest point of light in the sky, 1.4° to the right of its brighter companion. The gap will grow a bit, to 5°, by week’s end. The two appear about 20° high in the west a half-hour after sunset and don’t dip below the horizon until 10:45 p.m. local daylight time. A telescope shows both of their disks: Jupiter’s measures 32" across while Venus’ spans 34" and appears 32 percent lit.
Related: Jupiter joins Venus in the early eveningSaturday, July 4
No holiday better epitomizes summer in the United States than Independence Day. And the season’s namesake asterism — the Summer Triangle — will be on prominent display as fireworks ring out across the land. The trio’s brightest member, Vega in the constellation Lyra the Harp, stands nearly overhead in late evening. The asterism’s second-brightest star, Altair in Aquila the Eagle, then lies about halfway from the southeastern horizon to the zenith. Deneb, the luminary of Cygnus the Swan, marks the Summer Triangle’s third corner. Although it is this asterism’s dimmest star, it’s the brightest point of light in the northeastern sky.
Sunday, July 5
Asteroid 2 Pallas appeared opposite the Sun in mid-June, and it continues to linger in the sky all night. The magnitude 9.5 object — the second-largest body located between the orbits of Mars and Jupiter — lies among the background stars of Hercules, a region that climbs nearly overhead in late evening. Using binoculars or a telescope, first locate magnitude 3.1 Delta (δ) Herculis, the constellation’s third-brightest star. Pallas lies 0.6° southwest of this star tonight. If you are unsure which point of light is the asteroid, sketch the field and return to it a night or two later. The object that moved is Pallas.
The Moon reaches perigee, the closest point in its orbit around Earth, at 2:52 p.m. EDT. It then lies 228,101 miles (367,093 kilometers) away from us.
Pluto begins July 0.8° north-northeast of Xi2 (ξ2) Sagittarii and closes the month 0.3° north of it. This chart shows stars to magnitude 14.5.
Astronomy: Roen Kelly
Monday, July 6
Today marks the peak of Pluto’s 2015 appearance. The distant world reaches opposition, which means it lies opposite the Sun in our sky and remains visible all night. It glows dimly at magnitude 14.1, however, so you’ll need an 8-inch or larger telescope with good optics to spot it visually. Pluto currently lies in northern Sagittarius, some 0.7° east-northeast of magnitude 3.5 Xi2 (ξ2) Sagittarii. And don’t forget that the New Horizons spacecraft — set to fly past the dwarf planet in just eight days — already is returning sharper views of this world than humans have ever seen.
Tuesday, July 7
Mercury shines brightly in morning twilight this week, standing 7° high in the east-northeast a half-hour before sunrise today. The innermost planet shines at magnitude –0.7 and should show up nicely if you have an unobstructed horizon. If you can’t spot it right away, binoculars will bring it into view. Target the innermost planet through a telescope and you’ll see its 6"-diameter disk, which appears approximately two-thirds lit.
Today marks the peak of Pluto’s 2015 appearance. The distant world reaches opposition, which means it lies opposite the Sun in our sky and remains visible all night. It glows dimly at magnitude 14.1, however, so you’ll need an 8-inch or larger telescope with good optics to spot it visually. Pluto currently lies in northern Sagittarius, some 0.7° east-northeast of magnitude 3.5 Xi2 (ξ2) Sagittarii. And don’t forget that the New Horizons spacecraft — set to fly past the dwarf planet in just eight days — already is returning sharper views of this world than humans have ever seen.
Related: Hunt the last planetIf you ever thought the Sun’s distance controlled temperatures here on Earth, today should convince you otherwise. At 4 p.m. EDT, our planet reaches its most distant point from the Sun during 2015. At this so-called aphelion, the two lie 94.5 million miles (152.1 million kilometers) apart, some 3.1 million miles (5.0 million km) farther away than they were at perihelion in early January. The Northern Hemisphere’s warm temperatures at this time of year arise because the Sun passes nearly overhead at noon; during winter, the Sun hangs low in the sky.
Tuesday, July 7
Mercury shines brightly in morning twilight this week, standing 7° high in the east-northeast a half-hour before sunrise today. The innermost planet shines at magnitude –0.7 and should show up nicely if you have an unobstructed horizon. If you can’t spot it right away, binoculars will bring it into view. Target the innermost planet through a telescope and you’ll see its 6"-diameter disk, which appears approximately two-thirds lit.
The Moon's ever-changing face offers something for every amateur astronomer.
Jamie Cooper
Wednesday, July 8
Last Quarter Moon occurs at 4:24 p.m. EDT. It doesn’t rise in the east until around 1 a.m. local daylight time, however, by which time North American observers might notice that its phase has dwindled to 45 percent lit. Earth’s only natural satellite appears against the relatively inconspicuous background stars of the constellation Pisces the Fish.
Thursday, July 9
Venus peaks at magnitude –4.7 this evening, shining brighter than at any other time during this evening apparition. (The difference is essentially imperceptible, however — it appears only a thousandth of a magnitude brighter today than it did yesterday or will tomorrow.) As the inner planet swings closer to a direct line between the Sun and Earth, its telescopic appearance changes quickly. Tonight, Venus’ disk spans 37" and appears 27 percent lit.
Friday, July 10
Beautiful Saturn reached opposition and peak visibility in late May, and it remains a spectacular sight from nightfall until it sets around 2:30 a.m. local daylight time. It currently lies among the background stars of eastern Libra and appears highest in the south during late twilight. The ringed planet shines at magnitude 0.3 and is the brightest object in this part of the sky. When viewed through a telescope, the planet shows an 18"-diameter disk surrounded by a dramatic ring system that spans 41" and tilts 24° to our line of sight.
Last Quarter Moon occurs at 4:24 p.m. EDT. It doesn’t rise in the east until around 1 a.m. local daylight time, however, by which time North American observers might notice that its phase has dwindled to 45 percent lit. Earth’s only natural satellite appears against the relatively inconspicuous background stars of the constellation Pisces the Fish.
Thursday, July 9
Venus peaks at magnitude –4.7 this evening, shining brighter than at any other time during this evening apparition. (The difference is essentially imperceptible, however — it appears only a thousandth of a magnitude brighter today than it did yesterday or will tomorrow.) As the inner planet swings closer to a direct line between the Sun and Earth, its telescopic appearance changes quickly. Tonight, Venus’ disk spans 37" and appears 27 percent lit.
Friday, July 10
Beautiful Saturn reached opposition and peak visibility in late May, and it remains a spectacular sight from nightfall until it sets around 2:30 a.m. local daylight time. It currently lies among the background stars of eastern Libra and appears highest in the south during late twilight. The ringed planet shines at magnitude 0.3 and is the brightest object in this part of the sky. When viewed through a telescope, the planet shows an 18"-diameter disk surrounded by a dramatic ring system that spans 41" and tilts 24° to our line of sight.
Check the second-to-last star in the Big Dipper's handle. Most people will see it as double, while binoculars show this easily. The pair is called Mizar and Alcor, and they lie just 0.2° apart. A telescope reveals Mizar itself to be a double.
Jeff Dai
Saturday, July 11
The Big Dipper’s familiar shape lies high in the northwest as darkness falls these July evenings. One of the summer sky’s finest binocular double stars marks the bend of the Dipper’s handle. Mizar shines at 2nd magnitude, some six times brighter than its 4th-magnitude companion, Alcor. Even though these two are not physically related, they make a fine sight through binoculars. (People with good eyesight often can split the pair without optical aid.) A small telescope reveals Mizar itself as double — and these components do orbit each other.
Sunday, July 12
The waning crescent Moon rises around 3 a.m. local daylight time this morning. Earth’s satellite lies next to the V-shaped Hyades — the large star cluster that forms the head of Taurus the Bull. The Moon stands just 2° northwest of 4th-magnitude Gamma (γ) Tauri, the star that forms the V’s tip, and 5° due west of 1st-magnitude Aldebaran.
The Big Dipper’s familiar shape lies high in the northwest as darkness falls these July evenings. One of the summer sky’s finest binocular double stars marks the bend of the Dipper’s handle. Mizar shines at 2nd magnitude, some six times brighter than its 4th-magnitude companion, Alcor. Even though these two are not physically related, they make a fine sight through binoculars. (People with good eyesight often can split the pair without optical aid.) A small telescope reveals Mizar itself as double — and these components do orbit each other.
Sunday, July 12
The waning crescent Moon rises around 3 a.m. local daylight time this morning. Earth’s satellite lies next to the V-shaped Hyades — the large star cluster that forms the head of Taurus the Bull. The Moon stands just 2° northwest of 4th-magnitude Gamma (γ) Tauri, the star that forms the V’s tip, and 5° due west of 1st-magnitude Aldebaran.
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