Planetary system · 1 known planet · Vulpecula

HD 189733

HD 189733 A

Its star: above the horizon after darkHighest after dark 20:20 · south · 61°

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Where is HD 189733?

Times for LondonChange city

Look south, about 61° up at 20:20 in Vulpecula. It sinks lower through the evening and sets at 04:15.

Rises: 11:49
Highest: 20:04
Sets: 04:15
Best after dark: 20:20 · 61°

Can I see HD 189733?

No. The planets of HD 189733 can’t be seen with the eye, binoculars or any amateur telescope: they are lost in their star’s light. What you can do is point toward the star.

From London tonight, the star HD 189733 is above the horizon after dark. It’s highest soon after dark, around 20:20, in the south at 61°.

Why is HD 189733 interesting?

HD 189733 has 1 known planet, discovered in 2005 by the primary transit method.

HD 189733 Ab is a giant planet that orbits in under five days: a “hot Jupiter”.

What can you see?

Eyes

Direction only

Not visible. The star is around magnitude 7.7.

Binoculars

A faint star in the same field as the Dumbbell Nebula.

Telescope

A star very close to the Dumbbell Nebula. The planets themselves can’t be seen with any backyard telescope.

What you’re likely to see, not what a space telescope photographs.

About

HD 189733 is an orange star about 63 light-years away, almost next to the Dumbbell Nebula in Vulpecula. Its planet, HD 189733 b, is a hot Jupiter that passes in front of the star every 2.2 days.

It is one of the most studied exoplanets. In 2013 Hubble measurements showed it would look deep blue, a color thought to come from high clouds containing silicate particles, and winds there are extremely fast. In 2024 the James Webb Space Telescope detected hydrogen sulfide in its atmosphere.

HD 189733 b is a little more massive than Jupiter and always keeps the same side facing its star, with a dayside that reaches roughly 1,000 °C. In 2007 it became the first exoplanet to have a temperature map made of its surface, using the Spitzer Space Telescope.

The star has a faint red-dwarf companion.

Because the host star is relatively bright and nearby, its planet is a favorite target for space telescopes studying exoplanet atmospheres.

The HD 189733 system

Known planets of HD 189733 (catalog values from exoplanet.eu)
Planet	Mass	Radius	Orbit	From star	Found	Method
HD 189733 Ab	1.14 M♃	1.14 R♃	2.22 days	0.031 AU	2005	Primary Transit

M⊕ / R⊕ = Earth masses / radii; M♃ / R♃ = Jupiter. Masses from radial velocity are often minimum masses. Data: The Extrasolar Planets Encyclopaedia, exoplanet.eu (CC BY 4.0).

Questions

Can I see HD 189733 b?

No. You can see its host star with binoculars, near the Dumbbell Nebula.

Is HD 189733 b really blue?

Measurements suggest it reflects mainly blue light, so it would look blue up close.

Another planetary systemTau Ceti Another planetary systemEpsilon Eridani 0° awayDumbbell Nebula 3° awayTelum GuideStargazing for beginners ToolMoon phase & visibility tool

Sources: The Extrasolar Planets Encyclopaedia (CC BY 4.0); star chart: Wikidata (CC0). Positions computed for your place and time with astronomy-engine. Data & Licences